An antenna device for relaying wireless communication is known (for example, see patent literature 1). The antenna device comprises an antenna unit, an transmitting receiving unit, and fixing means.
As an antenna unit, a parabola antenna is a representative example, but the antenna unit may be a flat antenna, etc.
The transmitting receiving unit is provided behind the antenna unit. The transmitting receiving unit incorporates a receiving circuit and a transmitting circuit, and is an electric circuit unit that modulates and demodulates signals as necessity requires. The transmitting receiving unit has a container box that becomes a housing, and an electric circuit contained in the container box. The transmitting receiving unit is connected to the back surface of the antenna unit. The transmitting receiving unit is also called an outdoor unit (ODU).
The fixing means is a means for installing the antenna device in a high place; for example, the fixing means may be a mounting bracket for mounting the antenna device to a pole.
The antenna device is for relaying wireless communication, therefore the antenna device must be provided at a location with a good unobstructed view of the surrounding areas. Thus, as a matter of course, the antenna device is often provided at a location outside, and in a high place. Therefore, the antenna device is necessarily exposed directly to the direct rays of the sun, wind and rain, and wind and snow.
Here, the transmitting receiving unit contains an electric circuit inside. The electric circuit contains extremely elaborate electronic parts, therefore if the electric circuit is affected by an external environment, a malfunction occurs in the antenna device. Therefore, the container box that becomes the housing of the transmitting receiving unit must be extremely rigid and extremely airtight.
The container box is made of iron or iron alloy to keep the container box sturdy. The container box comprises at least two parts that are fitted together, to contain the electric circuit inside. Much effort is devoted to how to enhance the airtightness of these fitting parts of the at least two parts. For example, the one of these fitting parts is formed to be convex and the other of these fitting parts is formed to be concave, and the one of these fitting parts and the other thereof are fitted together and sealed. Further, an airtight packing is set between the one of these fitting parts and the other thereof. In this way, a rigid and highly airtight container box is formed within the electric circuit contained.